OS 61 SF Assembly Problem
 

I was given an OS .61 SF engine. I guess it was originally a heli engine because it has a rectangular head. But it was previously used on an airplane and I want to use it on my Great Planes Seawind 60. I took it apart and replaced the bearings with new generic bearings. I reassembled it, put a prop on it and realized it was tight and would no longer turn over. I figured out the problem. But I'm not sure what's causing the problem. When tightening the prop, the prop hub it being compressed against the front of the crank case. Initially I thought maybe I bought the wrong bearing. But I think now it's the right bearing. I'm wondering if there is supposed to be a washer between the prop hub and the bearing that I'm missing. I can't find an exploded view of it being that it's is so old. The other question I have has to do with the crankshaft key. It's the usual half moon shape, but one end is flat. I'm thinking that flat end goes towards the front. I think that's the way it was. But I'm not sure. Any input would be appreciated. Thanks

Just a guess, but it may be that your bearings aren't quite seated. Heat on the case, an old prop, and a big wrench to tighten the prop really tight may fix it all up.....
All precautions apply - don't melt/burn things, wear heavy gloves....

This was my first thought also. If you don't have the manual, go to the OS web site and download the manual/instructions for the .61SF. It should have an exploded diagram in there for you to see where and how the parts go back together.

I figured out my problems. My friend got the engine from someone else and never actually ran it himself. I pulled the hub on another OS 61 I have and realized that there is a washer between the hub and the bearing. I now know the first owner had hub off and lost the washer because the key was backwards when I got the engine. It was protruding slightly out of the hub. By putting it flat side forward it sits flush. I think the hub is thicker on my other .61 because it's key doesn't have a flat end. I just have to find a washer the right size now.

The SF engines are so old that they aren't even on the OS discontinued list on their website. If you know a link for the manual it would be appreciated.

Yes! you should have a washer between the Hub and front Bearing. all my OS 50 and 61 2st had them.

Jim